wifi: mac80211: consider aql_tx_pending when checking airtime deficit

When queueing packets for a station, deficit only gets added once the packets
have been transmitted, which could be much later. During that time, a lot of
temporary unfairness could happen, which could lead to bursty behavior.
Fix this by subtracting the aql_tx_pending when checking the deficit in tx
scheduling.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Link: https://lore.kernel.org/r/20220625212411.36675-3-nbd@nbd.name
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index a615cad..0509486 100644 (file)
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3800,6 +3800,13 @@ out:
 }
 EXPORT_SYMBOL(ieee80211_tx_dequeue);
 
+static inline s32 ieee80211_sta_deficit(struct sta_info *sta, u8 ac)
+{
+       struct airtime_info *air_info = &sta->airtime[ac];
+
+       return air_info->deficit - atomic_read(&air_info->aql_tx_pending);
+}
+
 struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
 {
        struct ieee80211_local *local = hw_to_local(hw);
@@ -3830,7 +3837,7 @@ struct ieee80211_txq *ieee80211_next_txq(struct ieee80211_hw *hw, u8 ac)
                struct sta_info *sta = container_of(txqi->txq.sta,
                                                    struct sta_info, sta);
                bool aql_check = ieee80211_txq_airtime_check(hw, &txqi->txq);
-               s32 deficit = sta->airtime[txqi->txq.ac].deficit;
+               s32 deficit = ieee80211_sta_deficit(sta, txqi->txq.ac);
 
                if (aql_check)
                        found_eligible_txq = true;
@@ -3955,7 +3962,7 @@ bool ieee80211_txq_may_transmit(struct ieee80211_hw *hw,
                        continue;
                }
                sta = container_of(iter->txq.sta, struct sta_info, sta);
-               if (sta->airtime[ac].deficit < 0)
+               if (ieee80211_sta_deficit(sta, ac) < 0)
                        sta->airtime[ac].deficit += sta->airtime_weight;
                list_move_tail(&iter->schedule_order, &local->active_txqs[ac]);
        }